Aminoplasts are defined herein and in the claims as an A-stage class of thermosetting resin based on the reaction of an amine with an aldehyde and the related acetals containing amines or amides. The most commercially used aldehyde is formaldehyde, and the most important amines are urea and melamine. They are used in molding, adhesives, laminating, textile finishes, permanent-press fabrics, wash-and-wear apparel fabrics, protective coatings, paper manufacture, leather treatment, binders for fabrics, foundry sands, graphite resistors, plaster-of-paris fortification, foam structures, and ion-exchange resins. A significant structural component of an aminoplast resin is the amino group to which is bonded at least one alkylol or alkylol ether or ester functional group. Those functional groups enter into condensation (heterolytic) reactions and provide the leaving groups for the reaction. The aminoplast typically provides at least two of such amino groups per molecule and one or two functional groups per amino group. The condensation reaction can generate a low to moderate molecular weight polymer (as would occur in making a B-stage resin), a highly crosslinked polymer (as would occur in making a thermoset C-stage resin) by homopolymerization or copolymerization, or it can generate a modification of the resin that either provides other type functionality or eliminates such functionality from the resin. For example, a starting monomer that contains the amino group with an associated methylol or methylol ether or ester group can be partially condensed and modified with a monomer that possesses, in addition, different functionality (such as ethylenic unsaturation) and such partial modification allows the aminoplast to be dimerized, oligomerized or polymerized by a homolytic reaction through such different functionality to form aminoplasts with a plethora of methylol and/or methylol ether and/or ester groups. This same result can be achieved by different route, by having the skeleton of the aminoplast possess other functional groups that can enter into heterolytic or homolytic reactions. For example, methacrylamide can be reacted with formaldehyde to form an aminoplast, and through the unsaturation, polymerization can be effected to create a linear polymer with pendant methylol or methylol ether or ester functional groups. Illustrative of such aminoplasts are the following: ##STR2## wherein R is hydrogen, alkyl containing 1 to about 4 carbon atoms, and acyl containing 1 to about 4 carbon atoms; R.sub.0 is alkyl of from 1 to about 4 carbon atoms, aryl, cycloalkyl, and the like; R.sub.1 is alkyl of from 1 to about 4 carbon atoms; and x is 0 or 1, and y is at least 2.
The RO- functionality of such aminoplasts provide the leaving groups of the alkylol (e.g., methylol) or alkylol ether or ester (e.g., methylol ether or ester) functional groups. Alkylol (e.g., methylol), alkylol ether (e.g., methylol ether) or alkylol ester (e.g., methylol ester) groups can condense with themselves to form ROH volatile compounds or water. They can condense with complementary functional groups, such as compounds containing active hydrogen groups, e.g., primary and secondary amines, carboxylic acids, alcohols, phenols, mercaptans, carboxamides (including amides from urea, thiourea), and the like.
Most aminoplasts contain a minor amount of dimer and oligomer products. These products are formed in the making of the aminoplast and represent precondensation between aminoplast monomers. The dimer and oligomer products contain substantially more -OR functionality than the aminoplast monomer.
As noted above, aminoplasts are used to form thermoset resin structures. Because they contain at least two RO- functional groups, they are used to react in systems that contain at least two complementary functional groups. Frequently, aminoplasts are added to resin formulations as one of many components. In such embodiments, there are no perceptible step-wise reactions between the aminoplast and any other component of the formulation. In such situations, it is not feasible to determine with any degree of accuracy as to which of the specific components of the formulation the aminoplast reacts.
The term "associative thickener" is art recognized to mean a nonionic hydrophobically modified water-soluble polymer capable of interacting in aqueous solution with itself and with other species such as latex particles. Typically they are made by polymerizing polyethylene oxide prepolymers with isocyanates. Mono-ols or diols with large aryl, alkyl, or aryl/alkyl groups are included to provide the hydrophobic modification. They are described in a number of patents. Hoy et al., U.S. Pat. No. 4,426,485, patented Jan. 17, 1984, broadly describes these materials as "a water-soluble, thermoplastic, organic polymer . . . having segments of bunched monovalent hydrophobic groups." This patent, in its "Description of the Prior Art," discusses a major segment of the prior art, and without endorsing the conclusions therein stated, reference is made to such description to offer a background to this invention.
The two Emmons et al. patents, U.S. Pat. No. 4,079,028 and U.S. Pat. No. 4,155,892, patented Mar. 14, 1978 and May 22, 1979, respectively, describe polyurethane associative thickeners that contain hydrophobic groups interconnected by hydrophilic polyether groups. The thickeners are nonionic.
There are a number of commercial associative thickeners based on the descriptions of the Hoy et al. and Emmons et al. patents.
Background on the use of thickeners in waterborne polymer systems, including those embraced in the characterization of this invention is set forth in the extensive literature on the subject, such as U.S. Pat. Nos. 4,426,485, 4,155,892, 4,079,028; 3,035,004; 2,795,564; 2,875,166 and 3,037,952, for example. The polymeric thickeners of this invention are also suitable as substitutes for the polymeric thickeners in the polymeric systems disclosed in U.S. Pat. Nos. 2,875,166 and 3,035,004 and in Canadian Pat. No. 623,617.
For the purposes of this invention and the discussion of the prior art, the skeletal unit of the aminoplast is the structure of the aminoplast minus the RO- leaving groups bonded to alkylene of the alkylol or alkylol ether or ester of the aminoplast, regardless of whether any of the RO- groups are removed from the aminoplast. That skeletal unit is referred to herein and in the claims as "Amp."
In the following description and in the claims hereof, the term "water dispersible," as such relates to aminoplast containing compositions and precursors to such compositions, that are water soluble or mechanically dispersible in water in a stable particulate form. A stable particulate form is one that retains its chemical characteristics after an extended period of time. It can be mechanically mixed in such particulate form in water, for an extended period of time at normal ambient conditions.
The term "linear," when used herein and in the claims to characterize a polymer, relates to a polymer that is devoid of crosslinking or branching that renders the polymer solid and cured. A "wholly linear" polymer is a polymer that is devoid of crosslinking and branching. A linear polymer may or may not be a wholly linear polymer.
The symbols and designations used herein are intended to be consistently applied, especially as used in formulations and equations, unless specifically stated otherwise.